Project Summary This project will validate two high throughput human blood-based DNA damage assays and develop them into commercial kits. The assays monitor types of damage associated with important human diseases. Whereas the PIG-A assay reports on gene mutation, the micronucleated reticulocyte (MN-RET) assay is responsive to chromosomal breaks and/or losses. The biomarkers are applicable to both humans and laboratory animals and will fulfill two important needs: extension of findings in laboratory animal models to direct studies in humans, and performance of well-controlled mechanistic laboratory studies to understand observations first made in humans. The assays utilize immunomagnetic separation prior to flow cytometry to dramatically enrich the relevant cell populations and thereby enhance assay precision and sensitivity. By providing simple-to-use kits with thoroughly documented reproducibility and inter-laboratory transferability, and validating the biomarkers for specific uses, researchers will have available tools with unprecedented efficiencies for comprehensively studying those factors that contribute to inter-individual differences in human DNA damage. Applications include the study of drug treatments, host and/or life-style factors that contribute to inter-individual differences in DNA damage and repair, exaggerated sensitivities to anti- neoplastic therapies, and population-based epidemiology studies of environmental exposures, including occupational exposures. The project benefits from a strong multidisciplinary team of internationally recognized scientists with a proven track record of successfully converting research advances into reliable commercial assay kits.